What Is Fineness Modulus of Sand?

What is Fineness Modulus of Sand?

Fineness modulus of aggregate is an index number which gives an idea about the finance of aggregate and is an approximate proportion of the average size of particle in the aggregate. It is found out by sieve analysis test of standard size in the laboratory. The thumb rule is lower the fineness modulus, particles are smaller and higher the fineness modulus, particles are larger.


What is Fineness Modulus of Sand?

Objective

To determine the fineness modulus of fine aggregate.

Equipment and Apparatus 

1. Set of sieve
2. Weighing machine                                           
3. Tray
4. Sand Specimen

Procedure
  1. Take s suitable sample of fine aggregate and take the weight of it.
  2. Now place the sample in the set of IS sieves arrange in descending order  10 mm, 4.75 mm, 2.36mm, 1.18 mm, 600 microns,  300 microns and 150 microns.
  3. Now put the lid at the top of IS sieve set and put the complete assembly in a sieve shaker and shake it for 15 minutes.
  4. After proper sieving fraction of sand of different sizes will be retained on different sieves.
  5. Take the weight of each fraction and note down it in the observation sheet.

Observation

For example,

Weight of Sample = 2000 gm.    Specification : IS: 383 - 1970

IS Sieve Designation
Weight of sample retained(gm)
Cumulative weight of  retained (gm)
Cumulative % of weight retained
 % of weight Passing
10mm
00
00
00
100
4.75 mm
22
22
1.1
98.9
2.36 mm
112
134
6.7
93.3
1.18 mm
200
334
16.7
83.3
600 microns
290
624
31.2
68.8
300 microns
1112
1732
86.6
13.4
150 microns
222
1954
97.7
2.3
Pan
46
2000
100
0

Note -

1. Cumulative % of weight retained = Cumulative weight of retained / Sample weight  × 100

2. % of weight Passing  =  (100 - Cumulative % of weight retained)

Fineness modulus  =  (Summation of cumulative % of weight                                                     retained up to 150 microns) / 100

                                =             240/100

                                =              2.4

So, in our case, it is Fine Sand.

Value of fineness Modulus of  Sand

Type of Sand
Fineness Modulus
Fine sand
2.2 – 2.6
Medium Sand
2.6 – 2.9
Coarse Sand
2.9 – 3.2

Zone of Sand As Per IS: 383-1970

IS Sieve
Zone 1
Zone 2
Zone 3
Zone 4
10 mm
100
100
100
100
4.75 mm
90 – 100
90 – 100
90 – 100
90 – 100
2.36 mm
 60 – 95
75 – 100
85 – 100
95 – 100
1.18 mm
30 – 70
55 – 90
75 – 100
90 – 100
600 microns
15 – 34
35 – 59
60 – 79
80 – 100
300 microns
5 – 20
8 – 30
12 – 40
15 – 50
150 microns
0 - 10
0 - 10
0 - 10
0 - 15


By percentage of weight Passing, we can find out the zone of sand by comparing the value from the table listed above. In our case, it matches from zone 3.

Weight of  Sample As Per IS: 2386 (Part - 1) - 1963

Maximum size present in substantial proportion in (mm)
Minimum weight of the sample to be taken for sieving in (Kg)
63
50
50
35
40 – 31.5
15
25
5
20 – 16
2
12.5
1
10
0.5
6.3
0.2
4.75
0.2
2.36
0.1

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